Apparatus for crimping yarn suitable for producing crepe fabrics



Dec. 3, 1968 J. A. FLOWERS ET AL 3,413,696

APPARATUS FOR CRIMPING YARN SUITABLE FOR PRODUCING CREPE FABRICS Filed Aug 11, 1966 nited States Patent 3,413,696 APPARATUS FOR CRIMPING YARN SUITABLE FOR PRODUCING CREPE FABRICS James Ashton Flowers, New Castle, and Donald Charles Knodel and John Edward Pretka, Wilmington, Del, assignors to E. I. du Pont de Nernours and Company, Wilmington, Del., a corporation of Delaware Filed Aug. 11, 1966, Ser. No. 571,787 4 Claims. (Cl. 281) ABSTRACT OF THE DISCLOSURE A stutfer-box crimping apparatus, having an improvement comprising a weighted pin afiixed to a mercury switch to signal any change in the mass of crimped filaments in the crimping chamber. The force applied in particular ranges produces crimped yarn suitable for the production of crepe fabric.

This invention relates to the production of continuous filament polyester yarns suitable for crepe fabrics, and more particularly, to a means for crimping continuous filament polyester yarns useful in making crepe fabrics.

The phenomenon of creping is largely due to the release of the latent torsional energy of highly twisted yarns. Conventionally, yarns having 50-100 turns per inch of either true or false twist are woven alternately 2 picks S-twist and 2 picks Z-twist to provide fabrics in which a random crepe is developed. Among the disadvantages of this method are slower speed yarn production, slower speed weaving with double shuttles, the requiremerit for specially adapted looms, the difiiculty of weavi;

ing lively high twist yarns and special fabric finishing conditions.

An object of this invention is to provide a novel apparatus for the manufacture of crepe-producing continuous filament polyester yarns. A further object is to provide continuous filament polyester yarns suitable for the production of crepe fabrics which contain little or no twist.

The objects of this invention are accomplished, in general, by providing in an apparatus for crimping continuous filament polyester yarns suitable for producing crepe fabrics which comprises feed roll means forming a nip to advance the continuous filament polyester yarns upwardly, a stuffer chamber adjacent the feed roll means and adapted to receive the yarns and to form a mass of crimped continuous filament polyester yarns of a predetermined magnitude therein and means to heat the stuffer chamber; the improvement comprising a pin curved to have an apex and upper and lower end portions, the pin being positioned so as to have the plane of the pin vertically aligned and to have its apex within the stuffer chamber so as to rest upon the yarn mass and the pin end portions spatially displaced and located outside the stuffer chamber, securing means at the upper pin end portion, a weight secured to the upper pin end portion by the securing means to thereby exert a force upon the yarn mass in the stuffer chamber, and mercury switch means operably associated with the lower pin end portion to signal any change in the predetermined magnitude of the yarn mass and means adapted to receive the signal and to control the feed roll means.

The embodiments of this invention and their advantages can be more readily understood by referring to the accompanying drawings.

FIGURE 1 is a diagrammatic view of one embodiment of the apparatus of this invention,

FIGURE 2 is an enlarged side elevation view of the curved pin and mercury switch shown in FIGURE 1,

FIGURE 3 is a front elevation view of the curved pin and mercury switch shown in FIGURE 2.

Referring to FIGURE 1, there is shown a diagrammatic view of the apparatus of this invention. Continuous filament polyester yarn 1 from any suitable yarn source, not shown, moves in the direction shown through guide 2 to the nip of feed roll means 3 and 4, which turn, respectively, in the direction shown. The terminology, feed roll means, as used herein, includes the feed rolls and conventional means for driving the feed rolls. Spatially displaced above feed roll means 3 and 4 is the crimping zone of stuifer chamber 5. The yarn 1 is directed into the stulfer chamber 5 against the combined force of a mass of crimped yarn held compacted in the chamber and the force applied by curved pin 6. The force being applied by curved pin 6 may be changed by means such as the attachment of weights such as weight 8 on securing means, such as eyelet 19. Mercury switch means 10 is operably associated with curved pin 6 and in rigid mechanical relation with mounting bracket 9. In the terminal portion of the discharge end of stuffer chamber 5 is slot 7 which is designed to accommodate the vertical movement of curved pin 6. The stuffer chamber 5 is heated by conventional means 11, e.g., electrical heating means. Disposed adjacent the discharge end of stuffer chamber 5 are conventional take-up means, not shown, where the yarn is packaged.

Referring to FIGURE 2, there is shown an enlarged view of the curved pin 6 and mercury switch 10. Curved pin 6 comprises an apex portion 12, which is within the stuifer chamber 5, and spatially displaced end portions 13 and 14 which are outside of the stutter chamber 5. One end portion 13 is rigidly attached to the mounting bracket 9 which holds mercury switch 10. The mercury switch has contacts 15 connected to control the feed roll means 3 and 4 by circuitry not shown. Mercury switch 10 can be tilted by rotation about shaft 17. Mounting bracket 9 is connected by shaft 17 to holder 16. Nut 20 and threaded stud 21 fasten holder 16 to support 18 in a manner which allows the holder to be moved in the slot in support 18.

Referring to FIGURE 3, a front elevation view more clearly shows the relation of the mercury switch, mounting bracket and holder.

The operation is described hereinafter. Continuous filament polyester yarn 1 is forwarded upwardly through guide 2 and into the nip of feed roll means 3 and 4. Crimping is caused to occur in crimper chamber 5 which is heated and a mass of crimped continuous filament polyester yarns of the magnitude desired is built up within stuffer chamber 5. The apex portion 12 of curved pin 6 rests upon the top of the mass with the weight 8 being added as shown in FIGURES 1 and 2. Take-up means, not shown, remove the crimped continuous yarn from the discharge end of stuffer chamber 5 at a rate such that the predetermined mass in stuifer chamber 5 remains substantially constant. Mercury switch 10 contacts curved pin 6 and is in an on position. If the mass varies beyond certain limits, curved pin 6 is vertically displaced and mercury switch 10 goes off. By conventional means,

the drive means for feed rolls 3 and 4 are likewise turned oil. The take-up means continues to remove the crimped continuous yarn thereby decreasing the mass within the stuffer chamber 5, changing vertical displacement of curved pin 6 and moving the mercury switch 10 back into the on position. The terminology on and off is used to indicate the mercury switch means is associated with suitable circuitry to control the drive means for the feed rolls. Such circuitry may simply be an electrical circuit connecting the mercury switch to a solenoid switch, the solenoid switch being within another circuit connecting the power source and the drive means. This second circuit is closed when the mercury switch is in one position (i.e., the on position), and which is open when the mercury switch is in the other position (i.e., the off position). The predeterminedmagnitude of yarn remains essentially constant due to the above means of signaling any change in the magnitude and means controlling the feed roll means in response to the signal.

The weight of the curved pin bearing on the mass of filaments affects the character of the crimp imparted to the continuous filament polyester yarn which in turn at fects the creping propensity of woven fabric into which the crimped continuous filament polyester yarn is subsequently converted. In the particular apparatus in the examples which follow, it is shown that 'by using a force of between about 0.4 and about 4.6 grams per square centimeter, there are produced yarns having about 8 to 36 crimps per inch (3 to 14 crimps per cm.) and a crimp amplitude of about 0.01-0.05 inch (0.025-0.127 cm.). In general, increasing the Weight bearing on the curved pin increases the crimp frequency, decreases the crimp amplitude and produces an increase in the fineness of the crepe figure.

If the individual filaments of the yarn are crimped such that they are out of phase with respect to neighboring filaments, -a crepe fabric Will not be obtained. Accordingly, the integrity of the continuous filament polyester yarn bundle should be maintained during the crimping step. This may be accomplished by applying a light degree of interlace, for example, a pin count of about 50, or a low degree of twist, for example, about 2 turns per inch (0.8 turn per cm.). The pin count of a given interlaced yarn is determined 'by inserting a pin through the yarn bundle, sliding the yarn in one direction until a point of resistance is reached, sliding the yarn in the opposite direction until a second resistance point is reached and determining the distance between the two resistance points. The distance in inches is the pin count.

Also, the density of the mass of crimped continuous filament polyester yarn within the stuffer chamber should be maintained at a substantially constant level if the desired crimp character is to :be imparted to the yarn. This is accomplished by the weighted curved pin which is a component of a switch, e.g., of the mercury type which is highly sensitive to vertical displacement of the pin. The switch is also connected by suitable means to a power supply for the feed rolls. Any variation in the process which would tend to permit continuous filament polyester yarn to be fed to the stutter chamber at a rate faster than it is Withdrawn will cause the curved pin to be lifted, tilting the switch to the off position and stopping the feed rolls. As a consequence of this sensitive arrangement, the amount of yarn in the stuffer chamber under a given set of conditions, and hence, its density therein, will remain constant.

Fabrics woven from continuous filament tpolyester yarns having the required crimp character may have the appearance varying from that of essentially no crepe to that of a subdued crepe in the greige, i.e., as they come from the loom. Generally, the fabrics will contain the crepe producing yarns only as filling yarns; and the maximum crepe is developed during the conventional boil-off operation. However, the crepe producing yarn can be used as warp and/ or fill. Boil-off is the usual procedure employed in the treatment of greige goods to remove stains incurred during weaving as well as to remove sizes and lubricants with which the yarns are normally coated. Invariably, boil-01f is carried out in an aqueous bath which may, if desired, contain agents that promote cleansing, at a temperature near C. During this treatment, both the warp yarns and the filling yarns shrink and reorient to some degree and thus allow the yarns to shift and permit a greater portion of the filling yarns to work their way to the surface of the fabric and provide full development of the random crepe figure. Accordingly, it is believed necessary that continuous filament polyester yarns useful in this invention should shrink when exposed to an aqueous bath heated to a temperature of about 100 C., supply yarns having a shrinkage value between about 3 and about 15% being suitable.

The temperature in the stuffer chamber is important from both the standpoint of crepe development and also the dyeing uniformity of the resulting crimped yarn. For most purposes, the stufrer chamber should be heated to a temperature in the range of from about 154 C. to about 210 C. Suitable temperatures for setting the crimp in polyester yarn is known to those skilled in the art, and the actual temperature chosen will depend on the particular yarn being treated, the rate at which the yarn is treated, the length of the treating chamber and the like.

Other factors which afiect the type of crepe obtained are the total denier of the yarn, the denier per filament and the fabric construction. Other factors remaining constant, the higher the total denier and the higher the denier per filament of the yarn the coarser will be the resulting crepe. Also, a looser fabric construction results in a relatively coarser crepe. In general, yarns having a total denier between about 30 and 250 and having a denier per filament between about 1 and about 5 have been found to be satisfactory for most purposes.

This invention may be further illustrated by the following example although it is understood that this example is included merely for the purposes of illustration and is not intended to limit the scope of the invention. Unless otherwise indicated, all parts and percentages are by Weight.

Example A polyethylene terephthalate, continuous filament polyester yarn having a boil-off shrinkage of 11.4, a denier of 70 and 34 filaments is prepared for feeding to a heated stuffer chamber by interlacing to a pin count of 50, and inserting 2 turns per inch (0.8 turn per centimeter) of Z-twist. The stutter chamber comprises a metal tube and is provided with a slot for insertion of the weighted curved pin at its discharge end. The curved pin, as shown in FIGURE 3, is afiixed to a mercury switch. The mercury switch is connected to a power supply for the feed rolls in such a manner that a slight lifting of the curved pin tilts the switch which causes the power to the feed rolls to be cut off.

The operation is initiated by loading the stutter chamber to provide resistance for crimping and the crimping continued until the crimped yarn moves the pin and tips the mercury switch to the off position. The mercury switch is mounted in such a manner so as to have the pin exert only a small force on the yarn within the stutter chamber. The amount of force so exerted is determined to be approximately 0.25 g. per square centimeter. A S-gram weight is then placed on the pin and the force per unit area exerted on the yarn mass is approximately 1.4 grams per square centimeter. The force is determined using a tensiometer and the area is the cross-section of the stutter chamber. The feed rolls are started again and the yarn fed at a rate of 300 yards per minute (275 meters per minute), and the end of the now crimped yarn passed to a wind-up for packaging at a rate of 262 yards per minute (240 meters per minute). The yarn feed creates an upward force which is only slightly greater than the force necessary to overcome the yarns frictional contact with the walls of the stutter chamber. Due to this effect the force exerted by the pin is the only major unbalanced force on the yarn mass, and this force per unit area will be reasonably constant from top to bottom of the yarn mass in the stutter chamber. The crimped yarn has 24 crimps per inch (9.5 crimps per centimeter) and a crimp amplitude of 0.02 inch (.0508 centimeter). The yarn is then woven into a tafieta fabric using a '70 denier, 34 filament, continuous-filament polyethylene terephthalate warp yarn having a boil-off shrinkage of 11.4%. The fabric has 96 warp ends per inch (38 warp ends per centimeter) and 68 filling ends per inch (27 filling ends per centimeter). The greige fabric has a light crepe figure. The woven fabric is then immersed in an aqueous bath containing conventional agents for finishing polyester fabrics at a temperature of 100 C. for about 1 hour. The finished fabric has a completely randomized medium crepe figure. The fabric is dyed to a uniform color with no evidence of streaks. The yarn and fabric are shown as Run 4 in table below.

The above experiment is repeated in seven separate additional runs. The conditions under which those runs are made and the results obtained are shown in the table. Three of the runs are made using a slug instead of the pin. The slug is hollow, weighted and has a T- shaped cross-section. The slug rests on the mass of crimped continuous filament polyester yarn in the stutfer chamber with the resulting yarn being removed through the hollow passage in the slug. The slug is connected through a mechanical linkage to a solenoid which controls the feed rolls.

eating that a force in a specific range is required. The range of force/ area necessary to give a desired crepe characteristic was found to be between approximately 0.6 and 4.6 grams per square centimeter. These limits are related to the specific conventional apparatus used in this example. Although a range of weights (e.g., 2 to 20 grams) to give the desired properties can be stated for this particular apparatus, obviously routine experimentation can determine the range in an apparatus of diiferent dimensions (e.g., different pin or a larger stuifer chamber). Therefore, an absolute range of weights cannot be stated apart from a specific apparatus, but such a range is unique to each and a weight within such range must be used to obtain the desired crepe characteristics.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except to the extent defined in the followin g claims.

What is claimed is:

1. In an apparatus for crimping continuous filament polyester yarns suitable for producing crepe fabrics which comprises feed roll means forming a nip to advance said continuous filament polyester yarns upwardly, a stulfer chamber adjacent to said feed roll means and adapted to receive said yarns and to form a mass of crimped continuous filament polyester yarns of a predetermined magnitude therein and means to heat said stutter chamber; the improvement comprising a pin curved to have an apex and upper and lower end portions, said pin being positioned so as to have the plane of said pin vertically aligned and to have its apex within said stuifer chamber so as to rest upon said yarn mass and said pin end portions spa- TABLE Crimped yarn Crimping conditions Run Force applied 1 Type of crepe Crimps per inch Crimp amplitude, Weight Weight (g./sq. cm.)

(crirnps/cm.) inche s (cm.) type (gains) 8 (3.15) 0. 05 (0.127) 0. 5 0. 4 Coarse.

21 (8. 27) 0.01 (0. 025) 2 0. 6 Medium Coarse.

32 (12. 6) 0. 009 (0.023) 2. 2 0. 8 Strea y.

24 (9. 5) 0. 02 (0. 051) 5. 0 1. 4 Medium.

80 (31. 5) 0. 006 (0. 015) 7. 2 1. 8 Streaky slight crepe.

36 (14. 2) 0.015 (0.038) 20 4. 6 Medium fine.

100 (39. 9) 0.003 (0. 008) 2 0 Streaky, negligible crepe.

1 Approximate force per unit area appled to the surface of the crimped yarn mass in the chamber.

In Runs 5 and 7, two of the slug runs, the crimped yarn properties are approximate. There is a clearly discernible crimp in the individual filaments, but measurement of the crimp in the yarn bundle is only approximate. In any case, as is seen in the type of crepe, the yarn is not suited to the formation of a creped fabric.

Run 8, using a force of 8.5 grams per square centimeter, would not run.

As can be seen from the above table, the conventional slug having a weight similar to that of the weighted pin does not result in the desired crepe characteristics. The streaky type of crepe was not produced when the weighted pin was used. Only the runs using the pin weight type produced a desirable crepe fabric. An unweighted pin apparatus, similar to the apparatus being improved upon in the present invention, is shown in US. Patent No. 3,200,466 (Duga et al.). Duga et al. provides a control device which introduces no appreciable back pressure on the filaments. This is essentially the unweighted pin in the apparatus in the previous example before weighted is added to the pin. The mercury switch is mounted, in the example, so as to exert only a small force on the yarn within the stufier chamber (e.g., approximately 0.25 gram per square centimeter). Although Duga et al.s apparatus produces crimped yarns, it is nowhere indicated that such yarns can be used to form fabrics of desirable crepe.

The improved apparatus of the present invention does produce desirable crepe fabric. It is seen that the degree of crepe is notably changed by the amount of force, inditially displaced and located outside said stuffer chamber, securing means at said upper pin end portion, a weight secured to said upper pin end portion by said securing means to thereby exert a force upon said yarn mass in said stuifer chamber, and mercury switch means operably associated with said lower pin end portion to signal any change in said predetermined magnitude of said yarn mass.

2. The apparatus of claim 1 wherein said weight exerts a force per unit area of between about 0.6 and about 4.6 grams per square centimeter on said yarn mass.

3. In an apparatus for crimping continuous filament polyester yarns suitable for producing crepe fabrics which comprises feed roll means forming a nip to advance said continuous filament polyester yarns upwardly, a stuffer chamber adjacent to said feed roll means and adapted to receive said yarns and to form a mass of crimped continuous filament polyester yarns of a predetermined magnitude therein and means to heat said stuifer chamber; the improvement comprising a pin curved to have an apex and upper and lower end portions, said pin being positioned so as to have the plane of said pin vertically aligned and to have its apex within said stuffer chamber so as to rest upon said yarn mass and said pin end portions spatially displaced and located outside said stuffer chamber, securing means at said upper pin end portion, a weight secured to said upper pin end portion by said securing means to thereby exert a force upon said yarn mass in 7 8 said stuifer chamber, and mercury switch means operably References Cited associated with said lower pin and portion to signal any change in said predetermined magnitude of said yarn mass UNITED STATES PATENTS and means adapted to receive said signal and to control 2,760,252 8/1952 Shattuck 281 said feed roll means. 5 3,200,466 8/ 1965 Duga et a1 28-1 4. The apparatus of claim 3 wherein said weight exerts 3,353,242 11/1967 Schrader 28-1 a force per unit area of between about 0.6 and about 4.6 grams per square centimeter on said yarn mass. LOUIS K. RIMRODT, Primary Examiner. 

